Jong's first children's book unfolds as the unnecessarily rambling, occasionally confusing monologue of a six-year-old girl whose parents are separated (""That means they still like each other, but they can't live together""). In credible kid jargon, Megan declares that ""divorce is dumb"" because she can never remember whether she left her underpants and barrettes at her mother's or her father's house and because ""you have to put up with your parents' other friends."" Her parents' respective lovers, in fact, figure prominently here: letting her imagination roam, Megan hatches drastic plots to dispose of them so her parents will get back together again. Jong adds the expected parental reassurance--Megan's mother and father both take her intermittent acting-out in stride, assuring her that their divorce is not her fault and that there is nothing she can do to change the situation. Yet the story is encumbered by many irrelevant digressions, among them a rundown of Megan's past nannies and the lovers they ""ran off"" with and the introduction of her father's secondary girlfriend, who on one visit even brings with her a new ""boy""--presumably yet another lover. As forthright as Jong's text, Tanz's two-color line art supplements Megan's words with some revealing details, encouraging youngsters to read between the lines. A sunny conclusion comes somewhat hastily, and more vigilant editing would have strengthened the book's impact--this is more successful as bibliotherapy than as storytelling. All ages. (Sept.)